Commit 1d734a3e authored by Matt Roper's avatar Matt Roper
Browse files

drm/xe: Name and document Wa_14019789679 



Early in the development of Xe we identified an issue with SVG state
handling on DG2 and MTL (and later on Xe2 as well).  In
commit 72ac3047 ("drm/xe: Emit SVG state on RCS during driver load
on DG2 and MTL") and commit fb24b858 ("drm/xe/xe2: Update SVG state
handling") we implemented our own workaround to prevent SVG state from
leaking from context A to context B in cases where context B never
issues a specific state setting.

The hardware teams have now created official workaround Wa_14019789679
to cover this issue.  The workaround description only requires emitting
3DSTATE_MESH_CONTROL, since they believe that's the only SVG instruction
that would potentially remain unset by a context B, but still cause
notable issues if unwanted values were inherited from context A.
However since we already have a more extensive implementation that emits
the entire SVG state and prevents _any_ SVG state from unintentionally
leaking, we'll stick with our existing implementation just to be safe.

Signed-off-by: default avatarMatt Roper <matthew.d.roper@intel.com>
Reviewed-by: default avatarJonathan Cavitt <jonathan.cavitt@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240812181042.2013508-2-matthew.d.roper@intel.com
parent d408d6f8

drivers/gpu/drm/xe/xe_lrc.c

+25 −10
Original line number Diff line number Diff line
@@ -5,6 +5,8 @@ 


#include "xe_lrc.h"



#include <generated/xe_wa_oob.h>



#include <linux/ascii85.h>



#include "instructions/xe_mi_commands.h"
@@ -24,6 +26,7 @@ 
#include "xe_memirq.h"

#include "xe_sriov.h"

#include "xe_vm.h"

#include "xe_wa.h"



#define LRC_VALID				BIT_ULL(0)

#define LRC_PRIVILEGE				BIT_ULL(8)
@@ -1581,19 +1584,31 @@ void xe_lrc_emit_hwe_state_instructions(struct xe_exec_queue *q, struct xe_bb *b 
	int state_table_size = 0;



	/*

	 * At the moment we only need to emit non-register state for the RCS

	 * engine.

	 * Wa_14019789679

	 *

	 * If the driver doesn't explicitly emit the SVG instructions while

	 * setting up the default LRC, the context switch will write 0's

	 * (noops) into the LRC memory rather than the expected instruction

	 * headers.  Application contexts start out as a copy of the default

	 * LRC, and if they also do not emit specific settings for some SVG

	 * state, then on context restore they'll unintentionally inherit

	 * whatever state setting the previous context had programmed into the

	 * hardware (i.e., the lack of a 3DSTATE_* instruction in the LRC will

	 * prevent the hardware from resetting that state back to any specific

	 * value).

	 *

	 * The official workaround only requires emitting 3DSTATE_MESH_CONTROL

	 * since that's a specific state setting that can easily cause GPU

	 * hangs if unintentionally inherited.  However to be safe we'll

	 * continue to emit all of the SVG state since it's best not to leak

	 * any of the state between contexts, even if that leakage is harmless.

	 */

	if (q->hwe->class != XE_ENGINE_CLASS_RENDER)

		return;



	switch (GRAPHICS_VERx100(xe)) {

	case 1255:

	case 1270 ... 2004:

	if (XE_WA(gt, 14019789679) && q->hwe->class == XE_ENGINE_CLASS_RENDER) {

		state_table = xe_hpg_svg_state;

		state_table_size = ARRAY_SIZE(xe_hpg_svg_state);

		break;

	default:

	}



	if (!state_table) {

		xe_gt_dbg(gt, "No non-register state to emit on graphics ver %d.%02d\n",

			  GRAPHICS_VER(xe), GRAPHICS_VERx100(xe) % 100);

		return;

drivers/gpu/drm/xe/xe_wa_oob.rules

+2 −0
Original line number Diff line number Diff line
@@ -35,3 +35,5 @@ 
		GRAPHICS_VERSION(2001)

22019338487_display	PLATFORM(LUNARLAKE)

16023588340	GRAPHICS_VERSION(2001)

14019789679	GRAPHICS_VERSION(1255)

		GRAPHICS_VERSION_RANGE(1270, 2004)